It had a tendency to make our dog Max kind of dopey and spaced out.  My wife didn't like that, but I figured it was better than the alternative of having him be restless and in pain.  It helped him get to sleep on nights that his post-op injury was hurting him.  As you can see from the replies on this thread, it affects different dogs in different ways.  If that's what your vet prescribes, then so be it.  But get him to recommend some other type of painkiller as a backup and have it on hand in case the Tramadol starts having negative effects on your dog.  And Moses might get lucky and handle it just fine.